This application corresponds to Japanese Patent Application No. 8-167530 filed on Jun. 27, 1996, which is hereby incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a high-voltage variable resistor used to adjust the focus voltage, screen voltage, etc. of a television receiver or like device.
2. Description of the Related Art
FIGS. 4 through 6 show the structure of an example of a conventional high-voltage variable resistor of the above-mentioned type. In this device, the connection between an electrode formed on a substrate and lead lines is possible without performing soldering. FIG. 4 is a sectional side view of a high-voltage variable resistor. FIG. 5 is an exploded perspective view showing a connection terminal holding structure. FIG. 6 is a sectional view showing the main components of a connection structure using a connection terminal.
As shown in FIG. 4, in this high-voltage variable resistor, an insulating substrate 2 formed of a ceramic material, such as alumina, is glued and fixed to a step section formed in the inner periphery of an insulating case 1 having one side open and formed of a synthetic resin. Rotation shafts 5 to which sliding members 4 are mounted are rotationally supported by cylindrical bearings 1a provided on the front side of the insulating case 1. An epoxy-type resin coating 3 is formed by molding on the open side of the insulating case 1 and on the back side of the insulating substrate 2 (which is shown on the upper side in the drawing).
A lead line holding cylinder 1b is provided on the insulating case 1, and a connection terminal accommodating section 6 is provided inside the insulating case 1 and at the base of the lead line holding cylinder 1b. The connection terminal accommodating section 6 accommodates a connection terminal 7, which is in contact with and electrically connected to a terminal electrode formed on the surface of the insulating substrate 2. An output lead line 8 for extracting a focus voltage and a screen voltage is inserted into the lead line holding cylinder 1b, and the lead line 8 inserted into this cylinder is connected to the connection terminal 7.
As shown in the enlarged views of FIGS. 5 and 6, the connection terminal 7 is formed by punching (e.g. stamping) the part out from a flat metal plate. The connection terminal 7 has a substantially rectangular lead line connecting section 7a at the center of which a plurality of holding members 7c are formed. The connection terminal 7 also includes a spring portion 7b bent into a curved configuration.
The spring portion 7b, which protrudes from the center of one side of the lead wire connecting section 7a toward the insulating substrate 2, is formed having a predetermined width which is smaller than the width of the lead line connecting section 7a in order to obtain the requisite elasticity.
The lead line connecting section 7a of the connection terminal 7 is held in a terminal holding groove 6a of the connection terminal accommodating section 6, and a part of the spring portion 7b is held in contact with an output terminal electrode 2a of the insulating substrate 2 and pressed against the insulating substrate 2. In this state, the connection terminal 7 is accommodated in the connection terminal accommodating section 6 and secured in position therein. A core wire 8a of the lead wire 8 inserted into the lead wire holding cylinder 1b is held by the holding members 7c to thereby provide electrical connection with the connection terminal 7.
Although not shown on the surface of the insulating substrate 2 (i.e., the lower surface thereof as seen in FIG. 4), there is formed an input terminal electrode to which high voltage is input, a grounding terminal electrode, an output terminal electrode for focus voltage and screen voltage, etc., and a resistor (e.g. film resistor) having a predetermined pattern. For example, the film resistor may comprise an arcuate variable resistor portion formed between the input terminal electrode and the grounding terminal electrode. One end of each sliding member 4 is arranged so as to slide on the variable resistor portion of the film resistor. Further, although not shown, lead terminals or lead wires for grounding and inputting high voltage are connected to the terminal electrodes by soldering, by contact with a conductive rubber member, or the like, and are led out from the open side of the insulating case 1.
However, in the above-described conventional high-voltage variable resistor, the connection terminal 7 and the terminal electrode 2a of the insulating substrate 2 are held in contact only at the limited surface region where the spring portion 7b contacts the terminal electrode 2a. Typically, this contacting surface region between the spring portion 7b and the terminal electrode 2a is quite small, and may form a limited contact line or point. When there exists insulating foreign matter such as adhesive material in the contact region between the connection terminal 7 and the terminal electrode 2a, the contact state becomes unstable, resulting in defective conduction, etc.